Our experience with 996 aspiration biopsies over a 2-year period is reported. Most of the specimens were obtained from breast (46%), lymph nodes (22%), and bone or soft tissue tumors (19%). Of 576 cases in which a diagnosis of malignant tumor was made, there was only one error (recognized on review as an error in judgment). In approximately 16% of the patients with cancer the aspirate was too scanty for a positive diagnosis and biopsy was necessary, emphasizing the need for biopsy when sampling is poor or clinical suspicion is not confirmed by the aspiration specimen.